The provision of a coating on a substrate may generally be desirable for a variety of reasons including protection of the substrate and provision of desirable surface characteristics which the substrate material does not exhibit to the required degree. In the case of silicone hydrogel contact lenses, it is desirable that the surfaces of silicone hydrogel contact lenses are readily wettable by an aqueous liquid, such as tear fluid, and are capable of retaining an aqueous fluid layer which is beneficial for the comfort of the wearer. However, soft silicone hydrogel contact lenses typically have hydrophobic surfaces or at least some hydrophobic surfaces areas and are required to be subjected to surface treatment to render the surfaces wettable, hydrophilic, and less susceptible to depositions of proteins and/or lipids from the ocular environment. Also, the effect of surface treatment should be durable and the modified surfaces should exhibit thermal, oxidative and hydrolytic stability as well as resistance to formation of deposits from tear components and delamination caused by mechanical stress.
A known approach for modifying the hydrophilicity of a relatively hydrophobic contact lens material is through the use of a plasma treatment under low pressure. The term “plasma” denotes an ionized gas (e.g., created by electric glow discharge which may be composed of electrons, ions of either polarity, gas atoms and molecules in the ground or any higher state of any form of excitation, as well as of photons). This ionized gas is often called “low temperature plasma”. For a review of plasma polymerization and its uses reference is made to R. Hartmann “Plasma polymerisation: Grundlagen, Technik and Anwendung, Jahrb. Oberflachentechnik (1993) 49, pp. 283-296, Battelle-Inst. e.V. Frankfurt/Main Germany; H. Yasuda, “Glow Discharge Polymerization”, Journal of Polymer Science: Macromolecular Reviews, vol. 16 (1981), pp. 199-293; H. Yasuda, “Plasma Polymerization”, Academic Press, Inc. (1985); Frank Jansen, “Plasma Deposition Processes”, in “Plasma Deposited Thin Films”, ed. by T. Mort and F. Jansen, CRC Press Boca Raton (19); O. Auciello et al. (ed.) “Plasma-Surface Interactions and Processing of Materials” publ. by Kluwer Academic Publishers in NATO ASI Series; Series E: Applied Sciences, vol. 176 (1990), pp. 377-399; and N. Dilsiz and G. Akovali “Plasma Polymerization of Selected Organic Compounds”, Polymer, vol. 37 (1996) pp. 333-341. The known plasma treatment under low pressure includes plasma deposition, plasma-induced polymerization, plasma grafting, plasma oxidation, and the likes. Plasma treatment under low pressure haven been used in commercial products, for example, such as, Focus NIGHT & DAY™ and O2OPTIX™ (CIBA VISION), and PUREVISION™ (Bausch & Lomb). Advantages of a plasma coating, such as, e.g., those may be found with Focus NIGHT & DAY™, are its durability, relatively high hydrophilicity/wettability), and low susceptibility to lipid and protein deposition and adsorption. But, plasma treatment under low pressure of silicone hydrogel contact lenses may not be cost effective, because the preformed contact lenses must typically be dried before plasma treatment and because of relative high capital investment associated with plasma treatment equipment.
The present invention is primarily directed to improved coating processes and coatings for ophthalmic devices and other objects without pre-drying them.